Wearable Circuits Sintered at Room Temperature Directly on The Skin Surface for Health Monitoring.

Zhang, Ling; Ji, Hongjun; Huang, Houbing; Yi, Ning; Shi, Xiaoming; Xie, Senpei; Li, Yaoyin; Ye, Ziheng; Feng, Pengdong; Lin, Tiesong; Liu, Xiangli; Leng, Xuesong; Li, Mingyu; Zhang, Jiaheng; Ma, Xing; He, Peng; Zhao, Weiwei; Cheng, Huanyu

A soft body area sensor network presents a promising direction in wearable devices to integrate on-body sensors for physiological signal monitoring and flexible printed circuit boards (FPCBs) for signal conditioning/readout and wireless transmission. However, its realization currently relies on various sophisticated fabrication approaches such as lithography or direct printing on a carrier substrate before attaching to the body. Here we report a universal fabrication scheme to enable printing and room-temperature sintering of metal nanoparticle on paper/fabric for FPCBs and directly on the human skin for on-body sensors with a novel coating layer. Consisting of polyvinyl alcohol (PVA) paste and nanoparticle additives in the water, the novel coating layer reduces the sintering temperature. Together with the significantly decreased surface roughness, it allows for the integration of a submicron-thick conductive pattern with enhanced electromechanical performance. Various on-body sensors integrated with an FPCB to detect health conditions illustrate a system-level example.